Comparative Study on the Impact of Fiber Confinement in High-Performance Fiber-Reinforced Concrete on GFRP Bar Bond Durability: Comparison of UHPC and ECC

This paper examines the bond durability between high-performance fiber-reinforced concrete (HPFRC) and glass fiber-reinforced polymer (GFRP) bars under corrosive conditions. Two HPFRC mixes—engineered cementitious composites (ECC) and ultrahigh-performance concrete (UHPC)—were cast into 36 groups (108 specimens) and subjected to 360 days of accelerated corrosion in a 60°C water bath, then tested in pull-out. Results reveal that concrete strength and ductility critically affect fiber confinement: in ECC, raising fiber content from 1.5% to 2.0% halves the peak slip and retains over 90% of initial bond strength, whereas in UHPC the same increase produces a 16% increase in slip and reduces residual strength to about 73%. A fiber-confinement coefficient K is proposed to capture this effect, and a predictive model based on K was developed, showing excellent agreement with experimental results. These findings provide practical guidance for the combined use of GFRP bars and HPFRC materials in corrosive environments and offer valuable insights for engineers and practitioners seeking durable solutions for structural applications.